Seeinstructions): Natural selection is the most powerful concept in the biology of species and ecosystems. In recent years, the principles and mechanisms of evolution have become vital to the molecular sciences as well. Many problems in human health are now recognized as being rooted in processes of molecular mutation and selection. Furthermore, a growing number of techniques inspired by biological evolution are becoming available to produce new molecular function by evolutionary means in the laboratory. Evolution at the molecular scale in both biology and chemistry is the subject of this unique training program, which is of great importance to the future of biotechnology. We focus neither on the origin of life nor on evolution at the organism level, the two traditional areas of interest in evolutionary biology. Rather, we emphasize the application of the principles and mechanisms of mutation, selection, and feedback to three areas: (1) the immune system as Nature's chief engine for rapid molecular evolution;(2) molecular evolution in host-pathogen interactions;and (3) the development and application of new tools for molecular evolution in the laboratory. The training program begins with a graduate-level course ("Chemical and Biological Principles of Evolution"), and includes the following additional features: (a) literature reviews and seminar series run by the students, (b) a yearly introduction to research by the faculty, (c) an annual program retreat, (d) intensive cross-disciplinary interactions including monthly scientific meetings of investigators in the above three general areas, and access of all trainees to all participating laboratories, (e) construction and updating by both students and faculty of a reference text, technical manual, and web-based open access resource, (f) training in safety and scientific ethics, (g) industrial internships for all students, and (h) periodic review by a panel of distinguished outside experts. Within this framework, trainees have extensive exposure to visiting investigators and to faculty and coworkers in many participating laboratories, giving them both a broad and deep perspective on this exciting field. RELEVANCE (Seeinstructions):